42 THE SKELETON OF THE CAT. 
Nasal Bone. Os nasale (Fig. 30).—The nasal bones {fill 
the space between the nasal process of the premaxillary, the 
frontal process of the maxillary, and the nasal spine 
of the frontal bone (Fig. 39,7). They thus form 
part of the dorsal wall of the nasal cavity near the 
middle line. 
Each may be described as consisting of two 
elongated triangular lamellz, one vertical, the other 
horizontal. The vertical lamella is curved slightly 
@ Fis. 3°. ventrad and has its apex directed craniad. It is 
ASAL BONE, 5 é e s 
Doxsau applied by its medial surface against the vertical 
See lamella of the opposite bone, the two thus forming 
a median vertical partition, the nasal crest (Fig. 43, 12), which 
extends ventrad into the nasal cavity and, by joining the dorsal 
edge of the lamina perpendicularis, helps to form the internasal 
septum. 
The horizontal lamella is attached to the dorsal margin of 
the vertical lamella in such a way that its apex lies opposite 
the base of the vertical lamella. It helps to roof in the nasal 
cavity, and by its base forms a part of the dorsal boundary of 
the narial opening. By its lateral margin it articulates with 
the nasal spine of the frontal at its caudal end, with the frontal 
process of the maxillary at its middle, and with the nasal process 
of the premaxilla at its cranial end. The lateral angle of its 
base projects in a curved line which forms the dorsal part of 
the lateral boundary of the narial opening. 
From the lateral border of the horizontal lamella a bony 
plate curves ventrad and mediad, enclosing a narrow fossa which 
receives a part of the ethmoid. This is the concha nasalis 
superior (nasoturbinal bone). 
Ethmoid Bone. Os ethmoidale (Figs. 31 and 32).—The 
ethmoid bone closes in the cranial cavity at its cranial end and 
extends forward into the nasal cavity, which it largely fills. 
It consists of a median vertical portion, the lamina perpen- 
dicularis (Fig. 43, ~; Fig. 42, £), forming a part of the nasal 
septum, of two lateral portions made of thin sheets of bone 
variously folded and united—the labyrinths (or ethmotur- 
binals), which fill the greater part of the nasal cavity; and of. 
